程序是获取用户输入的一个字符串,然后将其逆转输出代码:import java.util.Scanner;import java.util.Stack;public class ReverseString { public static void main(String[] args) { Scanner in = new Scanner(System.in); String string = in.next(); System.out.println(reString.strResult(string)); } }class reString{ public static String strResult(String str) { Stack<Character> reverseStr = new Stack<>(); for (int i = 0; i < str.length(); i++) { reverseStr.push(new Character(str.charAt(i))); } String reString = new String();// while (!reverseStr.isEmpty()) { reString += reverseStr.pop(); } return reString; }} 当reString = new String 程序可以正常运行,如输入uyfky输出ykfyu可是如果reString = null 的话,输入uyfky输出就成了nullykfyu 我想知道null为什么会在输出中?
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